Butyrylcholinesterases having an enhanced ability to hydrolyze acyl ghrelin

ABSTRACT

This document provides butyrylcholinesterases having an enhanced ability to hydrolyze acyl ghrelin as well as nucleic acids encoding such butyrylcholinesterases. This document also provides methods and materials for treating obesity and/or aggression. For example, methods for administering a nucleic acid encoding a wild-type or mutant butyrylcholinesterase having the ability to hydrolyze acyl ghrelin to a mammal under conditions wherein the level of acyl ghrelin within the mammal is reduced, under conditions wherein the rate of body weight gain of the mammal is reduced, under conditions wherein the mammal&#39;s level of aggression is reduced, and/or under conditions wherein the mammal&#39;s rate of developing stress-induced tissue damage are provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371 of International Application No. PCT/US2015/028141, having an International Filing Date of Apr. 29, 2015, which claims the benefit of U.S. Provisional Ser. No. 61/985,883 filed Apr. 29, 2014. This disclosure of the prior application is considered part of (and is incorporated by reference in) the disclosure of this application.

BACKGROUND

1. Technical Field

This document relates to butyrylcholinesterases (BChE) having an enhanced ability to hydrolyze acyl ghrelin as well as methods and materials for treating obesity and aggression. For example, this document provides nucleic acids encoding a butyrylcholinesterase having an enhanced ability to hydrolyze acyl ghrelin. In addition, this document provides methods and materials for using vectors (e.g., viral vectors) to express butyrylcholinesterases under conditions that reduce body weight within a mammal, reduce body weight gain in a mammal, reduce a mammal's level of aggression, reduce a mammal's response to cocaine, and/or reduce the severity of a stress-induced disability.

2. Background Information

Obesity is a medical condition where excess body fat accumulated to the extent that can cause a negative effect on health and/or lead to reduced life expectancy.

An aggressive behavior can be a behavior that is characterized by strong self-assertion with hostile or harmful tones. Aggressive behaviors can lead to various problems such as academic, employment, and relationship problems.

Stress-related disability is a growing problem in advanced countries with older populations.

SUMMARY

This document provides butyrylcholinesterases having an enhanced ability to hydrolyze acyl ghrelin. For example, this document provides nucleic acids that encode a butyrylcholinesterase polypeptide that (a) contains one or more amino acid mutations with respect to a wild-type butyrylcholinesterase polypeptide and (b) exhibits an elevated ability to hydrolyze acyl ghrelin with respect to the ability of that wild-type butyrylcholinesterase polypeptide. This document also provides methods and materials for treating obesity and/or aggression. For example, this document provides methods for administering a nucleic acid encoding a wild-type or mutant butyrylcholinesterase having the ability to hydrolyze acyl ghrelin to a mammal under conditions wherein the level of acyl ghrelin within the mammal is reduced, under conditions wherein the body weight of the mammal is reduced, under conditions wherein the body weight gain of the mammal is reduced, under conditions wherein the mammal's level of aggression is reduced, under conditions wherein the mammal's response to cocaine is reduced, and/or under conditions wherein the severity of a stress-induced disability is reduced. This document also provides methods for reducing stress-induced reactions by, for example, reducing the numbers of cells expressing “senescence-related markers” such as beta galactosidase.

As described herein, a nucleic acid can be designed to encode a polypeptide that includes the amino acid sequence set forth in FIG. 1 or the amino acid sequence set forth in FIG. 1 with one or more (e.g., two, three, four, five, or six) of the following amino acid substitutions: A199S, S227A, S287G, A328W, F329M, or Y332G (amino acid numbering starts after the signal sequence). In some cases, such a polypeptide can have an increased ability to hydrolyze acyl ghrelin as compared to a polypeptide having the amino acid sequence set forth in FIG. 1. In some cases, a nucleic acid can be designed to encode a polypeptide that includes the amino acid sequence set forth in FIG. 2 or the amino acid sequence set forth in FIG. 2 with one or more (e.g., two, three, four, five, or six) of the following amino acid substitutions: A199S, F227A, S287G, A328W, F329M, or Y332G (amino acid numbering starts after the signal sequence). In some cases, such a polypeptide can have an increased ability to hydrolyze acyl ghrelin as compared to a polypeptide having the amino acid sequence set forth in FIG. 2.

As also described herein, a wild-type or mutant butyrylcholinesterase or nucleic acid encoding a wild-type or mutant butyrylcholinesterase can be administered to a mammal (e.g., an obese human or an aggressive human) to reduce or control the body weight gain of that mammal, especially when, for example, that mammal has ready access to rich food (e.g., high calorie or high fat food), to reduce the aggressiveness of that mammal, and/or to reduce stress induced biochemical changes in body tissue. For example, a viral vector encoding a mutant butyrylcholinesterase having an enhanced ability to hydrolyze acyl ghrelin as compared to a wild-type human butyrylcholinesterase can be administered to a human to reduce the body weight of that human or to reduce the aggressiveness of that human or to protect that human from stress-related damage. In some cases, expression of a wild type or mutant BChE in vivo can reduce external and internal signs of aging and lower stress-induced tissue damage.

In general, one aspect of this document features a nucleic acid encoding a polypeptide having the amino acid sequence set forth in SEQ ID NO:3 with a F329M substitution (amino acid numbering starts after the signal sequence) or with a combination with one or more of the following amino acid substitutions: A199S, F227A, S287G, A328W, F329M, or Y332G (amino acid numbering starts after the signal sequence), wherein the polypeptide has an increased ability to hydrolyze acyl ghrelin as compared to a polypeptide having the amino acid sequence set forth in SEQ ID NO:3.

In another aspect, this document features a viral vector comprising a nucleic acid sequence that encodes a polypeptide having the amino acid sequence set forth in SEQ ID NO:3 with a F329M substitution (amino acid numbering starts after the signal sequence) or with a combination with one or more of the following amino acid substitutions: A199S, F227A, S287G, A328W, F329M, or Y332G (amino acid numbering starts after the signal sequence), wherein the polypeptide has an increased ability to hydrolyze acyl ghrelin as compared to a polypeptide having the amino acid sequence set forth in SEQ ID NO:3.

In another aspect, this document features a polypeptide having the amino acid sequence set forth in SEQ ID NO:3 with a F329M substitution (amino acid numbering starts after the signal sequence) or with a combination with one or more of the following amino acid substitutions: A199S, F227A, S287G, A328W, F329M, or Y332G (amino acid numbering starts after the signal sequence), wherein the polypeptide has an increased ability to hydrolyze acyl ghrelin as compared to a polypeptide having the amino acid sequence set forth in SEQ ID NO:3.

In another aspect, this document features a method for reducing the body weight of a mammal (e.g., a mammal having wild-type butyrylcholinesterase). The method comprises, or consists essentially of, administering a polypeptide or a nucleic acid encoding the polypeptide to the mammal, wherein the polypeptide comprises the ability to hydrolyze acyl ghrelin, and wherein the body weight of the mammal is reduced following the administration. The mammal can be a human. The method can comprise administering the polypeptide to the mammal. The method can comprise administering the nucleic acid to the mammal. The method can comprise administering a viral vector comprising the nucleic acid to the mammal. The viral vector can be an adeno-associated virus vector.

In another aspect, this document features a method for reducing the aggressiveness of a mammal (e.g., a mammal having wild-type butyrylcholinesterase). The method comprises, or consists essentially of, administering a polypeptide or a nucleic acid encoding the polypeptide to the mammal, wherein the polypeptide comprises the ability to hydrolyze acyl ghrelin, and wherein the aggressiveness of the mammal is reduced following the administration. The mammal can be a human. The method can comprise administering the polypeptide to the mammal. The method can comprise administering the nucleic acid to the mammal. The method can comprise administering a viral vector comprising the nucleic acid to the mammal. The viral vector can be an adeno-associated virus vector.

In another aspect, this document features a method for reducing the rate of aging in terms of external appearance and internal development of stress-induced tissue damage and biochemical and cellular changes characteristic of senescence in a mammal (e.g., a mammal having wild-type butyrylcholinesterase). The method comprises, or consists essentially of, administering a polypeptide or a nucleic acid encoding the polypeptide to the mammal, wherein the polypeptide comprises the ability to hydrolyze acyl ghrelin.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although methods and materials similar or equivalent to those described herein can be used to practice the invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a sequence listing of a wild-type mouse butyrylcholinesterase (SEQ ID NO:1) along with a nucleic acid sequence (SEQ ID NO:2) that encodes this wild-type mouse butyrylcholinesterase.

FIG. 2 is a sequence listing of a wild-type human butyrylcholinesterase (SEQ ID NO:3) along with a nucleic acid sequence (SEQ ID NO:4) that encodes this wild-type human butyrylcholinesterase.

FIGS. 3A-D. Deacylation of human ghrelin by human BChE. (A) One g of purified human BChE was analyzed by SDS-PAGE and stained with SYPRO-Ruby to confirm high purity (single major band). (B) One ng of human acyl-ghrelin was treated with different amount of human BChE. After 20 hours of incubation, residual acyl ghrelin and desacyl ghrelin in each reaction were determined. (C) One ng of human acyl ghrelin was treated with 10 g of human BChE and % decrease in residual acyl ghrelin was measured as a function of time. (D) Ten μg of human BChE was incubated for 10 minutes with 0, 10, or 100 μM of BChE inhibitor, iso-OMPA, or a proteinase inhibitor mixture containing 1 μM of aprotinin, 20 μM of leupeptin, and 15 mM of pepstatin A. Afterwards, 1 ng of human acyl ghrelin was added, and the reaction was incubated for 20 hours. The hydrolysis activities with butyrylthiocholine (BTCh) or acyl-ghrelin as substrates were determined by Ellman assay and acyl-ghrelin immunoassay, respectively. Data are normalized to the no inhibitor controls. All values are means±SD, each with duplicate samples (n=3).

FIG. 4. Circulating levels of acyl-ghrelin and desacyl-ghrelin in mice with gene transfer of native mouse BChE (mBChE wt) or mutated enzyme (mBChE mut). C57bl/6 mice at 12-week age were fasted for 20 hours, and serum samples were collected to determine the levels of acyl ghrelin and desacyl ghrelin. Samples from ad libitum fed mice served as controls. All values are means±SD (n=5 per group), ***, p<0.001 compared with other groups.

FIG. 5. Faster removal of ghrelin injected into mice with BChE gene transfer compared with a control gene transfer. Circulating acyl ghrelin levels after injection of 1 μg of recombinant human acyl ghrelin. Control 16-week old C57bl/6 mice and mice with gene transfer of AAV-Luc (control) or AAV-mBChE mut vector treatments were used. Acyl ghrelin levels in serum were determined 1, 3, and 10 minutes after injection. Serum samples from ad libitum fed mice served as basal levels. All values are means±SD (n=9).

FIG. 6. Selective inhibition of BChE increases acyl ghrelin levels in mice with AAV mBChE mut vector treatment. C57bl/6 mice with AAV-Luc or AAV-mBChE mut vector treatments (18-week old) received 40 mg kg⁻¹ of selective BChE inhibitor (iso-OMPA) or saline. All mice were then fasted for 6 hours, and serum samples were collected to determine (A) BChE activity versus the reference substrate (BTCh) and (B) the levels of acyl ghrelin. All values are means±SD, each with duplicate samples (n=4), ***, p<0.001 compared with saline group.

FIG. 7. Mouse models with high-expression levels of BChE by gene transfer. C57bl/6 mice were injected with AAV-Luc vector, AAV-mBChE wild type, or AAV-mBChE mutant vector at the dose of 1×10¹³ viral particles per mouse at 6-week age. Plasma samples were collected at the indicated time points and assayed for BTCh hydrolysis activity. All values are means±SD, each with triplicate samples (n=5 per group).

FIG. 8 is a graph plotting the weight gain of the indicated mice on normal diet and high fat (obesogenic) diet.

FIG. 9 is a graph plotting the number of fights per testing trial for the indicated mice.

FIG. 10 is a graph plotting the number of fights per testing trial for the indicated mice.

FIG. 11 is a graph plotting the number of fights per testing trial for the indicated mice.

FIG. 12 is a graph plotting the number of fights per testing trial for the indicated mice.

FIGS. 13A-D. Photomicrographs of fat cells in 22-month-old mice. A) Fad pad sample from untreated control mouse. Blue stain=beta-galactosidase activity, classic sign of cellular aging and senescence. B) Sample from same-age mouse given adenoviral vector for mutant mouse butyrylcholinesterase at age 1 month. Absence of blue stain indicates healthy cells. C) photograph showing the external appearance of 16 month old mice from indicated groups (c=control, v=vector). D) Survival curve showing early death of controls housed for 5 months under conditions of moderate stress.

DETAILED DESCRIPTION

This document provides butyrylcholinesterases having an enhanced ability to hydrolyze acyl ghrelin, nucleic acids encoding such butyrylcholinesterases, vectors (e.g., viral vectors) that contain nucleic acid encoding such butyrylcholinesterases, and methods and materials for treating obesity, aggression, or both. For example, this document provides nucleic acids encoding a butyrylcholinesterase having an enhanced ability to hydrolyze acyl ghrelin. In addition, this document provides methods and materials for using vectors (e.g., viral vectors) to express butyrylcholinesterases under conditions that reduce body weight gain within a mammal, that reduce a mammal's level of aggression, and/or that reduce stress that can lead to premature aging externally and internally, as well as increased risk of premature death. This document also provides methods and materials for using vectors to express wild type butyrylcholinesterases in greater than normal amounts under conditions that reduce body weight gain within a mammal, that reduce a mammal's level of aggression, and/or that reduce stress-induced tissue damage.

The polypeptides provided herein can be designed to include the amino acid sequence set forth in SEQ ID NO:1 or 3 or the amino acid sequence set forth in SEQ ID NO:1 or 3 with the exception that it contains one, two, three, four, five, or more amino acid additions, subtractions, or substitutions. For example, a polypeptide provided herein can have the amino acid sequence set forth in SEQ ID NO:3 with the following six changes: A199S, F227A, S287G, A328W, F329M, and Y332G. In some cases, a polypeptide provided herein can have the amino acid sequence set forth in SEQ ID NO:3 with a single F329M change. Other examples of polypeptides provided herein are set forth in Table 1. In some cases, a polypeptide provided herein can have an enhanced ability to hydrolyze acyl ghrelin as compared to a wild type human BChE having the amino acid sequence set forth in SEQ ID NO:3.

TABLE 1 Polypeptides based on human BChE. Mutations with respect to SEQ ID NO: 3 A199S, F227A, S287G, and A328W F329M A199S, F227A, S287G, A328W, and F329M

In some cases, a polypeptide provided herein can have an amino acid sequence with at least 85% (e.g., 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%) sequence identity to a reference sequence (e.g., SEQ ID NO:1 or 3). In some cases, a polypeptide provided herein can have an amino acid sequence with at least 85% (e.g., 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%) sequence identity to SEQ ID NO:1 or 3, provided that the amino acid sequence is not identical to the sequence set forth in SEQ ID NO:1 and 3. Percent sequence identity is calculated by determining the number of matched positions in aligned amino acid sequences (target amino acid sequence aligned to an identified amino acid sequence), dividing the number of matched positions by the number of amino acids of the identified amino acid sequence (e.g., SEQ ID NO:3), and multiplying by 100. A matched position refers to a position in which identical amino acids occur at the same position in aligned amino acid sequences. Percent sequence identity also can be determined for any nucleic acid sequence.

Percent sequence identity is determined by comparing a target amino acid sequence to the identified amino acid sequence (e.g., SEQ ID NO:3) using the BLAST 2 Sequences (Bl2seq) program from the stand-alone version of BLASTZ containing BLASTN version 2.0.14 and BLASTP version 2.0.14. This stand-alone version of BLASTZ can be obtained on the World Wide Web from Fish & Richardson's web site (fr.com/blast) or the U.S. government's National Center for Biotechnology Information web site (ncbi.nlm.nih.gov). Instructions explaining how to use the Bl2seq program can be found in the readme file accompanying BLASTZ.

Bl2seq performs a comparison between two sequences using either the BLASTN or BLASTP algorithm. BLASTN is used to compare nucleic acid sequences, while BLASTP is used to compare amino acid sequences. To compare two nucleic acid sequences, the options are set as follows: -i is set to a file containing the first nucleic acid sequence to be compared (e.g., C:\seq1.txt); -j is set to a file containing the second nucleic acid sequence to be compared (e.g., C:\seq2.txt); -p is set to blastn; -o is set to any desired file name (e.g., C:\output.txt); -q is set to -1; -r is set to 2; and all other options are left at their default setting. The following command will generate an output file containing a comparison between two sequences: C:\Bl2seq -i c:\seq1.txt -j c:\seq2.txt -p blastn -o c:\output.txt -q -l -r 2. If the target sequence shares homology with any portion of the identified sequence, then the designated output file will present those regions of homology as aligned sequences. If the target sequence does not share homology with any portion of the identified sequence, then the designated output file will not present aligned sequences.

For example, if (1) a target sequence is compared to the sequence set forth in a reference sequence that has 100 amino acid residues and (2) the Bl2seq program presents the target sequence aligned with a region of that sequence with the number of matches being 86, then the amino acid target sequence has a percent identity to that reference sequence that is 86 (i.e., 86÷100×100=86.0). It is noted that the percent identity value is rounded to the nearest tenth. For example, 78.11, 78.12, 78.13, and 78.14 are rounded down to 78.1, while 78.15, 78.16, 78.17, 78.18, and 78.19 are rounded up to 78.2. It also is noted that the length value will always be an integer.

A polypeptide provided herein can be produced using any suitable method, including recombinant technology. In some cases, a polypeptide provided herein can be a substantially pure polypeptide. As used herein, the term “substantially pure” with reference to a polypeptide means that the polypeptide is substantially free of other polypeptides, lipids, carbohydrates, and nucleic acid. In some cases, a substantially pure polypeptide can be a polypeptide that is at least 60 percent pure or is any chemically synthesized polypeptide. A substantially pure polypeptide can be at least about 60, 65, 70, 75, 80, 85, 90, 95, or 99 percent pure. Typically, a substantially pure polypeptide will yield a single major band on a non-reducing polyacrylamide gel.

In some cases, a polypeptide provided herein can be modified by linkage to a polymer such as polyethylene glycol (PEG), or by fusion to another polypeptide such as albumin, for example. For example, one or more PEG moieties can be conjugated to a polypeptide provided herein via lysine residues. Linkage to PEG or another suitable polymer, or fusion to albumin or another suitable polypeptide can result in a modified polypeptide having an increased half life as compared to an unmodified polypeptide. Without being bound by a particular mechanism, an increased serum half life can result from reduced proteolytic degradation, immune recognition, or cell scavanging of the modified polypeptide. Any appropriate method can be used to modify a polypeptide provided herein by linkage to PEG (also referred to as “PEGylation”) or other polymers including, without limitation, those described elsewhere (U.S. Pat. No. 6,884,780; Cataliotti et al., Trends Cardiovasc. Med., 17:10-14 (2007); Veronese and Mero, BioDrugs, 22:315-329 (2008); Miller et al., Bioconjugate Chem., 17:267-274 (2006); and Veronese and Pasut, Drug Discov. Today, 10:1451-1458 (2005). Examples of methods for modifying a polypeptide provided herein by fusion to albumin include, without limitation, those described elsewhere (U.S. Patent Publication No. 20040086976, and Wang et al., Pharm. Res., 21:2105-2111 (2004)).

Nucleic Acids, Vectors, and Host Cells

This document also provides nucleic acids encoding a polypeptide provided herein as well as expression vectors containing the nucleic acids, and host cells containing the nucleic acids and/or expression vectors. As used herein, the term “nucleic acid” refers to both RNA and DNA, including cDNA, genomic DNA, and synthetic (e.g., chemically synthesized) DNA. A nucleic acid molecule can be double-stranded or single-stranded (i.e., a sense or an antisense single strand). Nucleic acids include, for example, cDNAs encoding the chimeric polypeptides provided herein.

An “isolated nucleic acid” is a nucleic acid that is separated from other nucleic acid molecules that are present in a vertebrate genome, including nucleic acids that normally flank one or both sides of the nucleic acid in a vertebrate genome. The term “isolated” as used herein with respect to nucleic acids also includes any non-naturally-occurring nucleic acid sequence, since such non-naturally-occurring sequences are not found in nature and do not have immediately contiguous sequences in a naturally-occurring genome.

An isolated nucleic acid can be, for example, a DNA molecule, provided one of the nucleic acid sequences normally found immediately flanking that DNA molecule in a naturally-occurring genome is removed or absent. Thus, an isolated nucleic acid includes, without limitation, a DNA molecule that exists as a separate molecule (e.g., a chemically synthesized nucleic acid, or a cDNA or genomic DNA fragment produced by PCR or restriction endonuclease treatment) independent of other sequences as well as DNA that is incorporated into a vector, an autonomously replicating plasmid, a virus (e.g., a retrovirus, lentivirus, adenovirus, or herpes virus), or into the genomic DNA of a prokaryote or eukaryote. In addition, an isolated nucleic acid can include an engineered nucleic acid such as a DNA molecule that is part of a hybrid or fusion nucleic acid. A nucleic acid existing among hundreds to millions of other nucleic acids within, for example, cDNA libraries or genomic libraries, or gel slices containing a genomic DNA restriction digest, is not considered an isolated nucleic acid.

Isolated nucleic acid molecules can be produced using standard techniques, including, without limitation, common molecular cloning and chemical nucleic acid synthesis techniques. For example, polymerase chain reaction (PCR) techniques can be used to obtain an isolated nucleic acid containing a nucleotide sequence that encodes a BChE polypeptide. PCR refers to a procedure or technique in which target nucleic acids are enzymatically amplified. Sequence information from the ends of the region of interest or beyond typically is employed to design oligonucleotide primers that are identical in sequence to opposite strands of the template to be amplified. PCR can be used to amplify specific sequences from DNA as well as RNA, including sequences from total genomic DNA or total cellular RNA. Primers typically are 14 to 40 nucleotides in length, but can range from 10 nucleotides to hundreds of nucleotides in length. General PCR techniques are described, for example in PCR Primer: A Laboratory Manual, ed. by Dieffenbach and Dveksler, Cold Spring Harbor Laboratory Press, 1995. When using RNA as a source of template, reverse transcriptase can be used to synthesize complementary DNA (cDNA) strands. Ligase chain reaction, strand displacement amplification, self-sustained sequence replication, or nucleic acid sequence-based amplification also can be used to obtain isolated nucleic acids. See, for example, Lewis (1992) Genetic Engineering News 12:1; Guatelli et al. (1990) Proc. Natl. Acad. Sci. USA 87:1874-1878; and Weiss (1991) Science 254:1292.

Isolated nucleic acids also can be chemically synthesized, either as a single nucleic acid molecule (e.g., using automated DNA synthesis in the 3′ to 5′ direction using phosphoramidite technology) or as a series of oligonucleotides. For example, one or more pairs of long oligonucleotides (e.g., >100 nucleotides) can be synthesized that contain the desired sequence, with each pair containing a short segment of complementarity (e.g., about 15 nucleotides) such that a duplex is formed when the oligonucleotide pair is annealed. DNA polymerase is used to extend the oligonucleotides, resulting in a single, double-stranded nucleic acid molecule per oligonucleotide pair, which then can be ligated into a vector.

Isolated nucleic acids (e.g., nucleic acids encoding a polypeptide provided herein) also can be obtained by mutagenesis. For example, a reference sequence (e.g., SEQ ID NO:2 or 4) can be mutated using standard techniques including oligonucleotide-directed mutagenesis and site-directed mutagenesis through PCR. See, Short Protocols in Molecular Biology, Chapter 8, Green Publishing Associates and John Wiley & Sons, edited by Ausubel et al., 1992.

Vectors containing nucleic acids such as those described herein also are provided. A “vector” is a replicon, such as a plasmid, phage, or cosmid, into which another DNA segment may be inserted so as to bring about the replication of the inserted segment. An “expression vector” is a vector that includes one or more expression control sequences, and an “expression control sequence” is a DNA sequence that controls and regulates the transcription and/or translation of another DNA sequence.

In the expression vectors, a nucleic acid (e.g., a nucleic acid encoding a polypeptide provided herein) can be operably linked to one or more expression control sequences. As used herein, “operably linked” means incorporated into a genetic construct so that expression control sequences effectively control expression of a coding sequence of interest. Examples of expression control sequences include promoters, enhancers, and transcription terminating regions. A promoter is an expression control sequence composed of a region of a DNA molecule, typically within 100 to 500 nucleotides upstream of the point at which transcription starts (generally near the initiation site for RNA polymerase II). To bring a coding sequence under the control of a promoter, it is necessary to position the translation initiation site of the translational reading frame of the polypeptide between one and about fifty nucleotides downstream of the promoter. Enhancers provide expression specificity in terms of time, location, and level. Unlike promoters, enhancers can function when located at various distances from the transcription site. An enhancer also can be located downstream from the transcription initiation site. A coding sequence is “operably linked” and “under the control” of expression control sequences in a cell when RNA polymerase is able to transcribe the coding sequence into mRNA, which then can be translated into the protein encoded by the coding sequence.

Suitable expression vectors include, without limitation, plasmids and viral vectors derived from, for example, bacteriophage, baculoviruses, tobacco mosaic virus, herpes viruses, cytomegalovirus, retroviruses, vaccinia viruses, adenoviruses, and adeno-associated viruses. In some cases, a viral vector can be virus particles such as type five adenovirus, helper-dependent adenovirus, adeno associated virus, measles virus, or lentivirus virus particles that are designed to express a wild type BChE polypeptide or mutant BChE polypeptide provided herein. Numerous vectors and expression systems are commercially available from such corporations as Novagen (Madison, Wis.), Clontech (Palo Alto, Calif.), Stratagene (La Jolla, Calif.), and Invitrogen/Life Technologies (Carlsbad, Calif.).

An expression vector can include a tag sequence designed to facilitate subsequent manipulation of the expressed nucleic acid sequence (e.g., purification or localization). Tag sequences, such as green fluorescent protein (GFP), glutathione S-transferase (GST), polyhistidine, c-myc, hemagglutinin, or Flag™ tag (Kodak, New Haven, Conn.) sequences typically are expressed as a fusion with the encoded polypeptide. Such tags can be inserted anywhere within the polypeptide including at either the carboxyl or amino terminus.

This document also provides host cells containing a nucleic acid or vector provided herein. The term “host cell” is intended to include prokaryotic and eukaryotic cells into which a recombinant nucleic acid or vector (e.g., an expression vector) can be introduced. As used herein, “transformed” and “transfected” encompass the introduction of a nucleic acid molecule (e.g., a vector) into a cell by one of a number of techniques. Although not limited to a particular technique, a number of these techniques are well established within the art. Suitable methods for transforming and transfecting host cells can be found, for example, in Sambrook et al., Molecular Cloning: A Laboratory Manual (2^(nd) edition), Cold Spring Harbor Laboratory, New York (1989). For example, calcium phosphate precipitation, electroporation, heat shock, lipofection, microinjection, and viral-mediated nucleic acid transfer can be used introduce nucleic acid into cells. In addition, naked DNA can be delivered directly to cells in vivo as described elsewhere (U.S. Pat. Nos. 5,580,859 and 5,589,466).

Compositions and Methods for Administration

A wild type BChE polypeptide or mutant BChE polypeptide provided herein, or a nucleic acid encoding a wild type BChE polypeptide or mutant BChE polypeptide provided herein, can be incorporated into a composition for administration to a mammal (e.g., an obese or aggressive human who is seeking treatment). For example, a viral vector designed to express a wild type BChE polypeptide or a mutant BChE polypeptide provided herein can be administered to a mammal (e.g., a human) under conditions wherein the body weight of the mammal, the rate of weight gain, and/or the level of aggressiveness of the mammal is reduced in a therapeutic manner. Compositions containing a wild type BChE polypeptide or mutant BChE polypeptide provided herein (or a nucleic acid encoding such a polypeptide) may be given once or more daily, weekly, monthly, or even less often, or can be administered continuously for a period of time (e.g., hours, days, or weeks). In some cases, preparations designed to stabilize such polypeptides may maintain effective activity in a mammal for several days. This document provides a viral vector or viral vectors designed to express a natural or mutant BChE polypeptide provided herein, which can be administered once to a mammal in a way that generates effective amounts of the polypeptide for months or years (e.g., two years or longer). In some cases, such treatment can be extended by later administration of an equivalent viral vector of altered serotype (e.g., type 8 adenoviral vector) to express the same polypeptide for extended treatments.

The polypeptide or nucleic acid to be administered to a mammal can be admixed, encapsulated, conjugated or otherwise associated with other molecules, molecular structures, or mixtures of compounds such as, for example, liposomes, receptor or cell targeted molecules, or oral, topical or other formulations for assisting in uptake, distribution and/or absorption. In some cases, a composition to be administered can contain a polypeptide or nucleic acid in combination with a pharmaceutically acceptable carrier. Pharmaceutically acceptable carriers include, for example, pharmaceutically acceptable solvents, suspending agents, or any other pharmacologically inert vehicles for delivering polypeptides, nucleic acids, or viral vectors (e.g., viral particles) to a subject. Pharmaceutically acceptable carriers can be liquid or solid, and can be selected with the planned manner of administration in mind so as to provide for the desired bulk, consistency, and other pertinent transport and chemical properties, when combined with one or more therapeutic compounds and any other components of a given pharmaceutical composition. Typical pharmaceutically acceptable carriers include, without limitation: water; saline solution; binding agents (e.g., polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g., lactose or dextrose and other sugars, gelatin, or calcium sulfate); lubricants (e.g., starch, polyethylene glycol, or sodium acetate); disintegrates (e.g., starch or sodium starch glycolate); and wetting agents (e.g., sodium lauryl sulfate).

Acceptable solvents for delivery of viral vectors include, without limitation, common physiological salt solutions such as 0.9% sodium chloride, or isotonic aqueous solutions of sodium phosphate buffered to a pH of 7.4.

Pharmaceutical compositions containing a polypeptide, nucleic acid, or viral vector as described herein can be administered by a number of methods including by subcutaneous, intrathecal, intraventricular, intramuscular, intraperitoneal, or intravenous injection.

The invention will be further described in the following example, which does not limit the scope of the invention described in the claims.

EXAMPLES Example 1—BChE Catalyzes Ghrelin Hydrolysis

A sample of purified human BChE was obtained from Dr. O. Lockridge and assessed by gel electrophoresis (FIG. 3A). The enzyme preparation resulted in a primary band for monomeric BChE and a secondary band for dimeric BChE (FIG. 3A).

No contaminants were detected. Incubation of a sample containing acyl ghrelin with increasing amounts of human BChE resulted in a decrease in the amount of acyl ghrelin and an increase in the amount of the breakdown product, desacyl ghrelin (FIG. 3B). A linear hydrolysis rate was observed (FIG. 3C). The hydrolysis of acyl ghrelin by human BChE was blocked by a BChE selective inhibitor (iso-OMPA) at the same concentration that blocks butyrylthiocholine (BTCh) hydrolysis (FIG. 3D). No inhibition of acyl ghrelin hydrolysis was observed using protease inhibitors (FIG. 3D). This is an example confirming that BChE has a well-developed capacity to metabolize ghrelin.

Example 2—In Vitro Screening Mutant Butyrylcholinesterases

Mutations of BChE

Human and mouse butyrylcholinesterase cDNAs were subjected to a series of amino acid substitutions in the region of the active site. Briefly, the steps were as follows. First, wild type mouse BChE cDNA or human BChE was cloned into a pAAV-CMV shuttle plasmid for a serotype 8 adeno-associated virus (AAV) gene transfer vector. A Kozak consensus sequence (GCCACC) was introduced before the translational start site. With this construct as template, site-directed mutagenesis using primers with specific base-pair alterations generated the desired sequences. The following mutants were made:

-   -   1. A328W (vs. human)     -   2. A328W/Y332A (vs. human)     -   3. F227A/S287G/A328W/Y332M (vs. human)     -   4. S227A/S287G/A328W/Y332M (vs. mouse)     -   5. A199S/A328W/Y332G (vs. human)     -   6. A199S/F227A/S287G/A328W/Y332G (vs. human BChE)     -   7. A199S/S227A/S287G/A328W/Y332G (vs. mouse BChE)     -   8. A199S/S287G/A328W/Y332A (vs. human)     -   9. F227A/S287G/A328W/Y332G (vs. human)     -   10. A199S/S287G/A328W/Y332G (vs. human)     -   11. F227A/S287G/A328W/Y332A (vs. human)     -   12. A199S/F227A/S287G/A328W/E441D (vs. human)     -   13. A199S/S227A/S287G/A328W/E441D (vs. mouse)     -   14. A199S/F227A/A328W/Y332G (vs. human)     -   15. A199S/F227A/S287G/A328W/Y332G/E441D (vs human)     -   16. A199S/S227A/S287G/A328W/Y332G/E441D (vs mouse)     -   17. F329M (vs. both)     -   18. A199S/F227A/S287G/A328W/F329M/Y332G (vs. human BChE)     -   19. A199S/S227A/S287G/A328W/F329M/Y332G (vs. mouse BChE)         Enzyme Screening Method

The A199S/F227A/S287G/A328W/Y332G (mutant human BChE) and the A199S/S227A/S287G/A328W/Y332G (mutant mouse BChE) enzymes were tested in vitro. For in vitro testing, HEK293 cells were transduced with AAV vector encoding the relevant enzyme cDNA, and enzyme was purified from culture supernatants by procainamide Sepharose column chromatography followed by ion-exchange chromatography. Purification led to a single major band on SDS polyacrylamide gel. Active sites were titrated with DFP to determine final molar enzyme concentration as described elsewhere (Geng et al., PloS-One, 8(6)e67446 (2013)). Samples were then tested with a commercial human ghrelin immunoassay kit to determine ghrelin hydrolyzing activity in vitro according to (a) a decrease in immunoreactive acyl ghrelin and (b) an increase in immunoreactive deacyl ghrelin.

The A199S/F227A/S287G/A328W/Y332G mutant human BChE exhibited modest activity, comparable to that of wild type human BChE, while the A199S/S227A/S287G/A328W/Y332G mutant mouse BChE exhibited enhanced activity (e.g., at least 20-fold more activity), comparable to that of wild type mouse BChE.

Example 3—Expression of a Mutant BChE In Vivo Reduces Acyl Ghrelin Levels and Increases Desacyl Ghrelin Levels

Method for Viral Vector Delivery of Recombinant Butyrylcholinesterase to Mice

Standard methods were used to introduce BChE cDNA into mice via hdAD and AAV viral gene transfer vectors. To produce and purify AAV8 viral particles, the plasmids pAAV-CMV-BChE (wt or mCocH) or pAAV-VIP-mCocH were co-transfected into HEK293T cells with helper vectors, pHelper and pAAV2/8, using FuGene HD Transfection Reagent (Roche). Three days later, AAV8 virus was purified from the cell lysates by ultracentrifugation against Optiprep Density Gradient Medium-Iodixanol (Sigma-Aldrich, St Louis Mo.). The concentration of viral particles was subsequently determined by real-time quantitative PCR (QPCR), which also was used to establish the tissue distribution of delivered vector.

Mutated BChE also was incorporated into a serotype-5 helper dependent adenoviral vector (hdAD) under regulation by a human ApoE hepatic control region (Kim et al., Proc. Natl. Acad. Sci. USA, 98:13282-13287 (2001)), with a bovine growth hormone polyadenylation sequence cloned into a derivative of the p281acZ hdAD-backbone plasmid. Vector was propagated using the AdNG 163 helper virus as described elsewhere (Parks et al., Proc. Natl. Acad. Sci. USA, 93:13565-13570 (1996)). Particle titers were then determined by optical density at 260 nm. Helper virus contamination, determined by plaque assay on HEK-293 cells, was 0.2% for both loaded and empty vectors.

Fed and fasting BALB/C mice (n=4) were injected with adeno-associated viral (AAV) vectors designed to express luciferase (control; AAV-Luc), wild-type mouse BChE (AAV-mBChE wt), or a mutant mouse BChE (AAV-mBChE mut). Uninjected mice (n=4) also were used as a control. The mutant mouse BChE had the sequence set forth in FIG. 1 with the following five amino acid substitutions: A199S/S227A/S287G/A328W/Y332G. Injection of AAV-mBChE mut resulted in a reduction in the plasma levels of acyl ghrelin and an increase in the plasma levels of desacyl ghrelin (FIG. 4). No significant effects were observed for the mice receiving AAV-Luc or AAV-mBChE wt (FIG. 4).

In another experiment, mice injected with either AAV-Luc or AAV-mBChE mut were injected intravenously with exogenous acyl ghrelin peptide (1 mg/mouse), and the levels of acyl ghrelin in plasma were measured 1, 3, and 10 minutes later. Mice injected with AAV-mBChE mut exhibited an increased ability to eliminate acyl ghrelin from plasma (FIG. 5).

In another experiment, plasma obtained from mice injected with either AAV-Luc or AAV-mBChE mut followed by injection with either saline or iso-OMPA was assessed for the ability to hydrolyze BTCh in vitro. Treatment with iso-OMPA abolished the BTCh hydrolysis activity observed in samples from mice receiving AAV-mBChE mut in the absence of iso-OMPA (FIG. 6). In addition, the level of acyl ghrelin in plasma for AAV-mBChE mut-treated mice receiving iso-OMPA was equivalent to the level observed in AAV-Luc-treated control mice (FIG. 6). These results demonstrate that the reduced acyl ghrelin levels in mice receiving gene transfer of mutant BChE are specifically due to BChE-driven catalysis of the active peptide.

In another experiment, C57bl/6 mice were injected with AAV-Luc vector, AAV-mBChE wild type, or AAV-mBChE mutant vector at the dose of 1×10¹³ viral particles per mouse at 6-week age. Plasma samples were collected at the indicated time points and assayed for BTCh hydrolysis activity, which was much higher in the samples from mice given BChE vectors than in mice given the luciferase (control) vector (FIG. 7). All values are means±SD, each with triplicate samples (n=5 per group).

These results demonstrate that BChE is capable of inactivating ghrelin and that appropriate mutations in the BChE active site can cause large increases in peptide hydrolyzing activity. These results also demonstrate that a high activity mutant can be expressed indefinitely in mice after a single injection of viral vector (2 years or more) and that mice given such vector can have a 90% reduction in levels of active ghrelin in blood plasma with no detectable adverse effect. Further, injected exogenous ghrelin disappears much faster in vector-treated mice than in control mice, and selective inhibition of BChE can prevent accelerated ghrelin destruction and can raise ghrelin levels, but protease inhibitors have no such effect.

Example 4—Expression of a Wild Type or Mutant BChE In Vivo Reduces Body Weight Gain

Controls were C57BL6 mice treated with AAV luciferase vector or no injection. The experimental group received either AAV wild type mouse BChE vector or AAV mutant mouse BChE vector as indicated in Example 3. Two sets of experimental and control mice were tested for weight gain (n=5 to 8). One set received normal laboratory mouse diet. The other set received a high fat diet with 45% of calories from fat over the observation periods of 12 to 16 weeks. Results are provided in FIG. 8.

Example 5—Expression of Wild Type or Mutant BChE In Vivo Reduces Aggressive Behavior

Controls were untreated or saline-treated mice (male Balb/C mice). The experimental group received the A199S/S227A/S287G/A328W/Y332G mutant mouse BChE by hdAD viral gene transfer (dose=1.7×10¹² viral particles i.v.), delivered at about 6 weeks of age. The numbers of fights per session on successive trials in the standard “resident-intruder” model were scored by treatment-blind observer. Plasma BChE activity and ghrelin levels (pre-fight) also were recorded.

Mice treated with the hdAD vector expressing mutant mouse BChE exhibited significantly reduced fighting compared with saline treated controls tested at 14-16 months of age (FIG. 9; p=0.003 by 2-way ANOVA). Mice treated with AAV vector encoding the same mutant mouse enzyme tested at 8 months of age also exhibited reduced fighting (FIG. 10; p=0.005). Plasma from these animals again revealed an about 100× increase in BChE levels and a substantial (50%) reduction in active ghrelin vs. saline controls and luciferase vector controls.

To prove that reduced ghrelin caused the reduce aggression, mice were treated with a mutant human BChE (“Mut 6 with C terminal truncation) AAV VIP mut6-C (10e13pt/mouse, n=10) that was poor at inactivating ghrelin. These mice were assessed using the aggression test at 15 to 16 month and exhibited no group difference with control (FIG. 11). Plasma from these animals exhibited a large increase in BChE activity vs. butyrylthiocholine (94-fold above control) and cocaine (still larger increase), but no reduction of acyl ghrelin (only a non-significant 15% decrease). The enzyme assays revealed a nearly 100-fold increase in BChE and a 92% drop in active ghrelin (Table 2). These results demonstrate that BChE-catalyzed loss of active ghrelin is involved in the anti-aggression effect of BChE gene transfer.

TABLE 2 Levels of active ghrelin (acyl ghrelin) and BChE activity in plasma samples collected at indicated ages from mice treated at about 6 weeks of age with the indicated viral gene-transfer expression vectors encoding the indicated enzymes. Controls received saline injections or vector encoding irrelevant protein (luciferase). Fasting acyl-ghrelin BChE level (U/mL) Vector Mean Mean x-fold vs Age treatment n (pg/ml) % control (U/ml) control ~15 month  hd-AD 7  62 ± 8.9 7.7%  60 ± 6.7  82 Mut 1 m-BChE ~15 month  Saline 10 801 ± 310 — 0.7 ± 0.03 10 month  AAV-8 10 177 ± 8.0  85% 18 ± 3.5  94 Mut6-h-BChE 10 month  saline 13 210 ± 18  — 0.2 ± 0.06 8 month AAV-8 5 78 ± 10 52% 197 ± 23  123 m-BChE 8 month Saline 7 339 ± 59  — 1.6 ± 0.04 3 month None 910 ± 65  154%  0.01 0% (BChE knockout) 1 month AAV-WT 5 308 ± 62  53% 558 ± 183  299 hBChE 3 × 10{circumflex over ( )}12 1 month AAV-F329M 2 109 ± 17* 19% 480 ± 77  257 mut hBChE 3 × 10{circumflex over ( )}12 1 month AAV-F329M 8  14 ± 8.5  8% 592 ± 80  540 Mut mBChE 10{circumflex over ( )}13 1 month saline 5 581 ± 120 1.9 ± 0.27 1.9

In another experiment, three month old C57/BL6 BChE knockout mice were tested for aggression. The knockout mice exhibited no detectable BChE and exhibited moderate elevation of ghrelin levels in the fed state (normal condition) and significantly higher aggression than wild-type mice of the same strain (FIG. 12).

Other Embodiments

It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims. 

What is claimed is:
 1. A nucleic acid encoding a polypeptide having the amino acid sequence set forth in SEQ ID NO:3 comprising an F329M substitution and optionally one or more additional amino acid substitutions selected from the group consisting of A199S, F227A, S287G, A328W, and Y332G with the numbering starting after the signal sequence of SEQ ID NO:3, wherein said polypeptide has an increased ability to hydrolyze acyl ghrelin as compared to a polypeptide having the amino acid sequence set forth in SEQ ID NO:3.
 2. The nucleic acid of claim 1, wherein said polypeptide comprises said additional A199S, F227A, S287G and A328W substitutions.
 3. The nucleic acid of claim 1, wherein said polypeptide comprises said additional A199S, F227A, S287G A328W, and Y332G substitutions.
 4. A viral vector comprising a nucleic acid sequence that encodes a polypeptide having the amino acid sequence set forth in SEQ ID NO:3 comprising an F329M substitution and optionally one or more additional amino acid substitutions selected from the group consisting of A199S, F227A, 5287G A328W, F329M, and Y332G with the numbering starting after the signal sequence of SEQ ID NO:3, wherein said polypeptide has an increased ability to hydrolyze acyl ghrelin as compared to a polypeptide having the amino acid sequence set forth in SEQ ID NO:3.
 5. The viral vector of claim 4, wherein said polypeptide comprises said additional A199S, F227A, S287G and A328W substitutions.
 6. The viral vector of claim 4, wherein said polypeptide comprises said additional A199S, F227A, S287G A328W, and Y332G substitutions.
 7. The viral vector of claim 4, wherein said viral vector is an adenoviral or adeno-associated viral vector. 